nvmet-auth: Diffie-Hellman key exchange support

Implement Diffie-Hellman key exchange using FFDHE groups for NVMe
In-Band Authentication.
This patch adds a new host configfs attribute 'dhchap_dhgroup' to
select the FFDHE group to use.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 157 insertions, 0 deletions

diff --git a/drivers/nvme/target/auth.c b/drivers/nvme/target/auth.c
index 5cdd23c34185..d5624bdf834b 100644
--- a/drivers/nvme/target/auth.c
+++ b/drivers/nvme/target/auth.c
@@ -54,6 +54,74 @@ int nvmet_auth_set_key(struct nvmet_host *host, const char *secret,
 	return 0;
 }
 
+int nvmet_setup_dhgroup(struct nvmet_ctrl *ctrl, u8 dhgroup_id)
+{
+	const char *dhgroup_kpp;
+	int ret = 0;
+
+	pr_debug("%s: ctrl %d selecting dhgroup %d\n",
+		 __func__, ctrl->cntlid, dhgroup_id);
+
+	if (ctrl->dh_tfm) {
+		if (ctrl->dh_gid == dhgroup_id) {
+			pr_debug("%s: ctrl %d reuse existing DH group %d\n",
+				 __func__, ctrl->cntlid, dhgroup_id);
+			return 0;
+		}
+		crypto_free_kpp(ctrl->dh_tfm);
+		ctrl->dh_tfm = NULL;
+		ctrl->dh_gid = 0;
+	}
+
+	if (dhgroup_id == NVME_AUTH_DHGROUP_NULL)
+		return 0;
+
+	dhgroup_kpp = nvme_auth_dhgroup_kpp(dhgroup_id);
+	if (!dhgroup_kpp) {
+		pr_debug("%s: ctrl %d invalid DH group %d\n",
+			 __func__, ctrl->cntlid, dhgroup_id);
+		return -EINVAL;
+	}
+	ctrl->dh_tfm = crypto_alloc_kpp(dhgroup_kpp, 0, 0);
+	if (IS_ERR(ctrl->dh_tfm)) {
+		pr_debug("%s: ctrl %d failed to setup DH group %d, err %ld\n",
+			 __func__, ctrl->cntlid, dhgroup_id,
+			 PTR_ERR(ctrl->dh_tfm));
+		ret = PTR_ERR(ctrl->dh_tfm);
+		ctrl->dh_tfm = NULL;
+		ctrl->dh_gid = 0;
+	} else {
+		ctrl->dh_gid = dhgroup_id;
+		pr_debug("%s: ctrl %d setup DH group %d\n",
+			 __func__, ctrl->cntlid, ctrl->dh_gid);
+		ret = nvme_auth_gen_privkey(ctrl->dh_tfm, ctrl->dh_gid);
+		if (ret < 0) {
+			pr_debug("%s: ctrl %d failed to generate private key, err %d\n",
+				 __func__, ctrl->cntlid, ret);
+			kfree_sensitive(ctrl->dh_key);
+			return ret;
+		}
+		ctrl->dh_keysize = crypto_kpp_maxsize(ctrl->dh_tfm);
+		kfree_sensitive(ctrl->dh_key);
+		ctrl->dh_key = kzalloc(ctrl->dh_keysize, GFP_KERNEL);
+		if (!ctrl->dh_key) {
+			pr_warn("ctrl %d failed to allocate public key\n",
+				ctrl->cntlid);
+			return -ENOMEM;
+		}
+		ret = nvme_auth_gen_pubkey(ctrl->dh_tfm, ctrl->dh_key,
+					   ctrl->dh_keysize);
+		if (ret < 0) {
+			pr_warn("ctrl %d failed to generate public key\n",
+				ctrl->cntlid);
+			kfree(ctrl->dh_key);
+			ctrl->dh_key = NULL;
+		}
+	}
+
+	return ret;
+}
+
 int nvmet_setup_auth(struct nvmet_ctrl *ctrl)
 {
 	int ret = 0;
@@ -81,6 +149,10 @@ int nvmet_setup_auth(struct nvmet_ctrl *ctrl)
 		goto out_unlock;
 	}
 
+	ret = nvmet_setup_dhgroup(ctrl, host->dhchap_dhgroup_id);
+	if (ret < 0)
+		pr_warn("Failed to setup DH group");
+
 	if (!host->dhchap_secret) {
 		pr_debug("No authentication provided\n");
 		goto out_unlock;
@@ -158,6 +230,14 @@ void nvmet_destroy_auth(struct nvmet_ctrl *ctrl)
 {
 	ctrl->shash_id = 0;
 
+	if (ctrl->dh_tfm) {
+		crypto_free_kpp(ctrl->dh_tfm);
+		ctrl->dh_tfm = NULL;
+		ctrl->dh_gid = 0;
+	}
+	kfree_sensitive(ctrl->dh_key);
+	ctrl->dh_key = NULL;
+
 	if (ctrl->host_key) {
 		nvme_auth_free_key(ctrl->host_key);
 		ctrl->host_key = NULL;
@@ -218,6 +298,21 @@ int nvmet_auth_host_hash(struct nvmet_req *req, u8 *response,
 	if (ret)
 		goto out_free_response;
 
+	if (ctrl->dh_gid != NVME_AUTH_DHGROUP_NULL) {
+		challenge = kmalloc(shash_len, GFP_KERNEL);
+		if (!challenge) {
+			ret = -ENOMEM;
+			goto out_free_response;
+		}
+		ret = nvme_auth_augmented_challenge(ctrl->shash_id,
+						    req->sq->dhchap_skey,
+						    req->sq->dhchap_skey_len,
+						    req->sq->dhchap_c1,
+						    challenge, shash_len);
+		if (ret)
+			goto out_free_response;
+	}
+
 	pr_debug("ctrl %d qid %d host response seq %u transaction %d\n",
 		 ctrl->cntlid, req->sq->qid, req->sq->dhchap_s1,
 		 req->sq->dhchap_tid);
@@ -315,6 +410,21 @@ int nvmet_auth_ctrl_hash(struct nvmet_req *req, u8 *response,
 	if (ret)
 		goto out_free_response;
 
+	if (ctrl->dh_gid != NVME_AUTH_DHGROUP_NULL) {
+		challenge = kmalloc(shash_len, GFP_KERNEL);
+		if (!challenge) {
+			ret = -ENOMEM;
+			goto out_free_response;
+		}
+		ret = nvme_auth_augmented_challenge(ctrl->shash_id,
+						    req->sq->dhchap_skey,
+						    req->sq->dhchap_skey_len,
+						    req->sq->dhchap_c2,
+						    challenge, shash_len);
+		if (ret)
+			goto out_free_response;
+	}
+
 	shash = kzalloc(sizeof(*shash) + crypto_shash_descsize(shash_tfm),
 			GFP_KERNEL);
 	if (!shash) {
@@ -365,3 +475,50 @@ out_free_tfm:
 	crypto_free_shash(shash_tfm);
 	return 0;
 }
+
+int nvmet_auth_ctrl_exponential(struct nvmet_req *req,
+				u8 *buf, int buf_size)
+{
+	struct nvmet_ctrl *ctrl = req->sq->ctrl;
+	int ret = 0;
+
+	if (!ctrl->dh_key) {
+		pr_warn("ctrl %d no DH public key!\n", ctrl->cntlid);
+		return -ENOKEY;
+	}
+	if (buf_size != ctrl->dh_keysize) {
+		pr_warn("ctrl %d DH public key size mismatch, need %lu is %d\n",
+			ctrl->cntlid, ctrl->dh_keysize, buf_size);
+		ret = -EINVAL;
+	} else {
+		memcpy(buf, ctrl->dh_key, buf_size);
+		pr_debug("%s: ctrl %d public key %*ph\n", __func__,
+			 ctrl->cntlid, (int)buf_size, buf);
+	}
+
+	return ret;
+}
+
+int nvmet_auth_ctrl_sesskey(struct nvmet_req *req,
+			    u8 *pkey, int pkey_size)
+{
+	struct nvmet_ctrl *ctrl = req->sq->ctrl;
+	int ret;
+
+	req->sq->dhchap_skey_len = ctrl->dh_keysize;
+	req->sq->dhchap_skey = kzalloc(req->sq->dhchap_skey_len, GFP_KERNEL);
+	if (!req->sq->dhchap_skey)
+		return -ENOMEM;
+	ret = nvme_auth_gen_shared_secret(ctrl->dh_tfm,
+					  pkey, pkey_size,
+					  req->sq->dhchap_skey,
+					  req->sq->dhchap_skey_len);
+	if (ret)
+		pr_debug("failed to compute shared secred, err %d\n", ret);
+	else
+		pr_debug("%s: shared secret %*ph\n", __func__,
+			 (int)req->sq->dhchap_skey_len,
+			 req->sq->dhchap_skey);
+
+	return ret;
+}